These we started from real potatoes. We left 4 small potatoes on the kitchen windowsill. They grew eyes similar to what you might find on an old batch of potatoes, only different (more purple and green rather than white). When I planted these, I cut the eyes out with about an inch of potato around. A few weeks later and tah-dah – the beginnings of potato plants!
I managed 6 plants from the cuttings – one is a tad bit small, but I think it’s okay.